Emergency trip mechanisms



Nv. 19, T957 J. B. STEVENS EMERGENCY TRIP MECHANISMS Filed Feb. 8.` 1952@h1/@Zay Jifby MHZZF bn/110714; MV

2,813,429 Patented Nov. 19, 1957 face United States Patent The presentinvention relates `to safety devices for valves, and more particularlyto emergency trip mechnisms for throttle and like valves.

In power plant practice, an emergency trip mechanism is normallyassociated with the throttle valve of a steam turbine. Under certainoperating conditions, the pull- Aout force, the force necessary toactuate the trip mechanism is' substantial. Consequently, the tripmechanism may be subject `to a Idelay in actuation due to this excessiveforce. `It is desirable `therefore to have the pullout force as' smallas possible, but it has been found that when this force is reduced belowa certain minimum, thetrip mechanism may be actuated inadvertently bypower plant vibrations transmitted to the mechanism `through pipes orthrough the building itself.

The present invention contemplates vibration-proof means whereby thepull-out force is relatively small and substantially constant under alloperating conditions, whereas the hooking force is high and steady, andis adjustable to `permit actuation of the mechanism by and only byapplication of a force of predetermined value.

More` specifically a primary object of my invention is to provide a tripmechanism wherein the pull-out force is essentially independent of theoperating conditions under which the valve may be requiredv to operate.

A further` object is to provide a trip mechanism of the stated classhaving novel means for regulating the pull-out force.

`These and other objects of the invention hereinafter appearing williind amplification in the attached specification, of which the attacheddrawings constitute a part. `In the drawings:

Fig. l is a side elevational View partially in section of a tripmechanism according to my invention;

Fig. 2 is a front elevational view of the mechanism;

Fig. 3 is a sectional view taken along the line 3-3 of Fig. l;

Fig. 4 is an enlarged fragmentary section view illustrating certainstructural features of the mechanism;

Fig. 5 is an enlarged sectional view taken along the line 5-5 of Fig. l;

Fig. 6 is a perspective view of one element of the mechanism; and

Fig. 7 is a fragmentary view illustrating a structural feature of mymechanism.

Referring more specilically to the drawings and particularly to Fig. l,the valve (not shown) is actuated by vertical movement of a stem 11which is threaded into a stern carriage 12 as indicated at 13. Thecarriage 12 is slidably mounted in a fixed sleeve 14, and is pivotallyattached by pins 16, 16, which extend through slotted openings 19, 19 inthe sleeve, to a latch arm 15, as illustrated in Fig. 7. The latch armis normally maintained in an elevated position by engagement with a hookassembly 17, hereinafter speciiically described. Counterclockwiserotation of the stem 11, by manual or other means not shown, willelevate said stern and disengage the valve head from its seat, therebyopening the valve.

Clockwise rotatiom on the other hand, will force the valve-head into itsseat elfecting closure of the valve. Upon actuation of the tripmechanism when the valve is open, the hook assembly 17 will be caused todisengage 'the latch arm 15 to allow downward movement of the carriage12 which will similarly eifect closure of the valve.

, The trip mechanism comprises in combination the hook assembly 17, thecarriage 12, an actuating spring 18, and the latch lever 15 which ispivotally attached at its right end to a collar 21 by a connecting link22. At the left hand side, lcollar 21 is bifurcated, and the spacedbifurcations 23, 23 are provided each with an upward projection 24. Thearms or bifurcations 23 carry a support bai 25 and the proec-tions v'24carry a limit bar 26.

The hook assembly 17 comprises a hook bracket 2S, which is pivotallyattached to the collar 21 through the medium` of a pin 27 to which thebracket is keyed, a connecting arm 29 iixed to the pin, a connecting rod31 pivotally attached to the upper end of the connecting arm 29, and ahook roller '32 rotatably mounted in the lower portion of the `hookbracket 28 as best shown in Figs.

t 4 and 5. The vhook bracket 28` as shown in Figs. 4 and 6 is formedwith a pair lof upwardly projecting ears 35 and 36 and an outwardlyextending arm 37 with an aperture 38 at the outer extremity thereof andan upstanding rounded lug i0 ateach-side of the aperture.

The hookfbracket 2S is resiliently connected to the `support bar 25 by aregulating bolt 33 co-acting with a regulating spring 34." The springtends to turn the hook bracket clockwise asview'ed in Fig. 1, but thebracket may be moved countercloc'kwise about its pivot 27 against thepressure oi the regulating spring 34 by actuation of the connectingrodl; Freedom for such movement is insured by mounting the bracket in apair of anti-friction bearings dll in the arms 23. The movement islimited to small angles by `Contact of the ears 35 and 36 with the limitbar 26. As illustrated in Fig. 4, the lower portion of the hook bracket2 8 is hollow; forming a lip 41 underlying the hook roller 32 which isrotatably mounted in `the bracket by means of a pair of anti-frictionbearings 42.` The hook roller may be mounted on the latch arm withoutdeparture from the present invention. In this arrangement the rollerwould engage the lip of hook bracket whereby the mechanism would operatein substaritally' the same `manner as the illustrated mechanism.

In the operation of the device, the valve (not shown) is opened bycounterclockwise rotation of the valve stem 11, thereby raising the stemin and with respect to the carriage 12 which is supported in an elevatedposition by engagement of the recessed end of the latch arm 15 with thehook roller 32 as described above. If a requirement arises for quickclosing of the valve, the connecting rod 31 is moved to the right toposition shown by the broken lines in Fig. 1. The resulting angularmovement of the bracket 28, limited by contact of the ear 36 with thelimit bar 26, swings the hook assembly 17 and therefore the hook roller32 out of engagement with the latch arm 15. This disengagement of thearm 15 permits the stem carriage 12 to move downwardly under pressure ofthe actuating spring 18, the pins 16, 16 sliding downwardly in therecesses 19, 19 of the sleeve 14, until the assembly assumes theposition shown in broken lines in Fig. l.

As recited above, the pull-out force of the conventional trip mechanismunder certain operating conditions is substantially greater than theforce required under normal conditions. This variation in pull-out forceis caused in large degree by internal unbalances acting on the stem andtransmitted to trip lever by a relatively high friction factor. In adevice according to the present in,

.ears which provides a constant bearing for the head over the entirerange of angular displacement of the hook bracket 28. A nut 43 isprovided on the regulating bolt 33 to conine the spring 34 between thesupport bar 25 and the nut 43. Tightening of thenut 43 will compress`the spring 34 and increase the force required to rotate the hookbracket 28 about its pivot 27, which by reason of the substantiallycomplete absence of friction in the hook assembly as a whole, is thepull-out force. By adjusting the nut 43 on the regulating bolt 33, thepullout force may be regulated with precision to a required minimumvalue without danger of inadvertent actuation by transitory impulsessuch as vibration.

While this invention is particularly adaptable to heavy duty valves, itis not contemplated that the device be limited to use on such valvesalone, and the invention may find useful application to other valves, orto mechanisms of similar nature and purpose.

l claim:

1. Emergency trip mechanism for valves, said mechanism comprising apivotally mounted pressure-biased valve-.supporting lever, a pivotedmember arranged to engage a free end of said lever and to support thelever in retracted position against said biasing pressure, means forapplying force from external source divorced from sai-d lever toangularly move said member about its pivot to release the said lever, aspring operatively connected to said member independently of the releasemeans and normally retaining the member in lever supporting position,said spring thereby acting in opposition to said release force whichapplied from the external source to move said member, means foradjusting the spring to regulate the pressure opposing the said releasemovement, and antifriction means affording a seat for the lever on saidmember. Y

2. Emergency trip mechanism for valves, said mechanism comprising apressure-biased valve-supporting member, a second member arranged toengage and support said valve-supporting member in retracted positionagainst said biasing pressure, means for applying force from externalsource divorced from said valve-supporting member to relatively displacesaid members from said engagement to permit movement of thevalve-supporting member to an advanced position by said pressure, aspring operatively associated with said members independently of theforce applying means and normally retaining the members in engagement,said spring thereby acting in opposition to said release force whenapplied from the external source to disengage the members, means foradjusting the spring to regulate the resistance thereon to said relativedisplacement, and antifriction means on one of said members forming aseat for the other member so as to reduce to a minimum the frictionopposing said displacement.

3. Emergency trip mechanism for valves, said mechanism comprising apressure-biased valve-supporting member constrained to move in arectilinear path, a lever having a pivotal connection intermediate itsends with said member and extending transversely to said path ofmovement of the latter, a pivotal support for one end of said lever, asecond lever pivotally supported adjacent the other end of the rst-namedlever and having thereon a seat for the proximate end of the latterwhereby to support the valve-supporting member in retracted positionagainst the said pressure bias, means for applying force from externalsource divorced from said rst-named lever to pivotally move said secondlever to displace the said seat in a direction approximatelylongitudinally of and away from the seated end of the rst-named lever tothereby release the latter, a spring operatively associated with saidsecond-named lever independently of the displacing means and normallyretaining said lever in operative position supporting the second-namedlever, said spring thereby acting in opposition to said release forcewhen applied from the external source to move said second lever, andmeans for adjusting the spring to reguylate the resistance thereof tosaid displacement.

References Cited in the le of this patent UNITED STATES PATENTS

